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Exit Activity Costs and Asset Impairments (Narrative) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014 facility	Dec. 31, 2013 facility	Dec. 31, 2012 facility
Restructuring and Related Activities [Abstract]
Number of consolidated facilities	2rock_NumberOfConsolidatedFacilities	2rock_NumberOfConsolidatedFacilities	2rock_NumberOfConsolidatedFacilities
Number of consolidated facilities to be closed	1rock_NumberofConsolidatedFacilitiestobeClosed
Expected future restructuring costs	$ 455us-gaap_RestructuringAndRelatedCostExpectedCost1

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- Definition

Number of Consolidated Facilities to be Closed

+ References

No definition available.

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- Definition

Amount expected to be recognized in earnings for the specified restructuring cost.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 420

-SubTopic 10

-Section 50

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6394359&loc=d3e17939-110869



Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 5

-Section P

-Subsection 3, 4



Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 420

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SAB Topic 5.P.4(b))

-URI http://asc.fasb.org/extlink&oid=27011515&loc=d3e140904-122747

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